1. Technical Field
The present specification relates to a semiconductor device, and more particularly, to a semiconductor device including a metal resistance element formed on a foundation insulating film and connected to contacts.
2. Discussion of the Background
In an analog integrated circuit, a resistance element is frequently used. Recently, the resistance element including a metal lamina, which is called a metal resistance element, draws increasing attention due to decreased temperature dependence of its resistance value.
In order to provide a highly integrated semiconductor device with increased resistance, many semiconductor devices include a thin metal resistance element with a thickness of about 500 Å or smaller.
One example of a related-art semiconductor device 50R including the metal resistance element is illustrated in FIGS. 1A to 1C, and FIG. 2. FIG. 1A is a plan view of the related-art semiconductor device 50R illustrating a position of formation of the metal resistance element. FIG. 1B is a sectional view of the related-art semiconductor device 50R along a line X-X shown in FIG. 1A. FIG. 1C is a sectional scanning ion microscope image of the related-art semiconductor device 50R shown in FIG. 1B.
As illustrated in FIG. 1B, on a silicon substrate 1R is provided an element separation oxidation film 3R. An interlayer insulating film 5R, a TEOS (tetra ethyl ortho silicate) film 11R, and a TEOS film 13R are sequentially formed thereon. On the TEOS film 13R are provided metal film patterns 15R to be connected to a metal resistance element 27R. A TiN (titanium nitride) film 17R is formed on the metal film pattern 15R.
Also, a TEOS film 19R and a TEOS film 23R are provided on the TEOS film 13R while covering the metal film pattern 15R, and have plane surfaces between the metal film patterns 15R.
Contact holes 25R are formed in the TEOS films 19R and 23R at positions corresponding to both ends of the metal resistance element 27R in a longitudinal direction of the metal resistance element 27R.
The metal resistance element 27R is provided on the TEOS film 23R and in the contact hole 25R and extends from an area between the contact holes 25R to an area in the contact holes 25R and above the metal film patterns 15R. Both ends of the metal resistance element 27R are electrically connected to the TiN films 17R and the metal film patterns 15R in the contact holes 25R.
A protection film 29R is provided on the TEOS film 23R and the metal resistance element 27R.
FIG. 2 is a schematic view of the related-art semiconductor device 50R during exposure of a resist film 33AR to light in order to form a resist film pattern for defining a formation of the metal resistance element 27R.
When the light is incident from a surface of the resist film 33AR as indicated by a downward arrow in FIG. 2 and passes through a CrSi film 27AR for forming the metal resistance element 27R and the TEOS films 23R, 19R, 13R and 11R, some of the incident light may be absorbed into the films or reflected as indicated by upward arrows in FIG. 2.
Generally, reflection of light occurs on interfaces between two substances having different indexes of refraction. Since the related-art semiconductor device 50R includes the various interlayer insulating films, reflection of light may repeatedly occur, which is called multiple reflections. For example, some of the incident light reflected on one interface may be reflected on another interface.
After the multiple reflections, some of the reflected light returning to a surface of the CrSi film 27AR interferes with the light reflected on the surface of the CrSi film 27AR and the incident light to generate a standing wave in the resist film 33AR. The standing wave generated by the reflected light and the incident light may affect patterning for forming the resist film pattern, that is, intensity of the standing wave may change a size of the resist film pattern.
Additionally, differences in thickness and quality (e.g., index of refraction, or the like) between the films may directly affect intensity of the light reflected on the interfaces between the respective films and the standing wave generated by the reflected light, resulting in substantial variations in the size of the resist film pattern for defining the formation of the metal resistance element 27R.
The variations in the size of the resist film pattern may vary a size of the metal resistance element 27R, resulting in a large variation in a resistance value of the metal resistance element 27R.